Flow range of flowmeter 1

[PAN]

The catalog indicate allowable momentary flow rate of the flowmeter. If the actual flow rate is higher than this value, what will be the side effects? Is this only the fault reading of flow rate?

This flowmeter can withstand 10 kg/cm2. The pump shut off pressure is less than this pressure.

Please advise me about the references for further study in this subject.

 

[quark]

The accuracy of flowmeters go down if you use them beyond the range for which they are designed for. The error in the reading may be anything and also the error may not be linear. Besides runaway or improper reactions, wastage of material, overflow and drainage you won't have any other critical side effects

Websites of Rosemount(now Emerson Process Control), Endress+Hauser, Foxboro and Yokagawa etc. will be helpful to you.

 

[bmsg]

What kind of flowmeter is this (that is, is it an orifice plate / venturi, magnetic flowmeter, turbine flowmeter, vortex flowmeter, etc)?

In the absence of the above information, what I can say is this:
1. If your flowrate is greater than the maximum your flowmeter will allow, go for a flowmeter with a greater range.
2. If your flowmeter can withstand a pressure which is higher than the shutoff pressure of your pump, then this is the correct thing to have.
But check whether the flowmeter has been calibrated at 10kg/cm2 (the error due to calibration at a pressure different from your line pressure will be significant if you are metering a gas - for liquids, the error is not an issue).

 

[PAN]

bmsg,

The flowmeter is OVAL Flowmeter (positive displacement type comprising a pair of oval gear rotors).

During normal operation, the flow will not be beyond the range of flowmeter. However, we worry about mis-operation due to the higher flow rate from pump.

The fluid is ethanol (liquid). We will be relocate this flowmeter from the other line. Then we do not want to buy the new flowmeter with a greater range.

 

[jsummerfield]

This sounds like a custody transfer or sales meter application. Accuracy is a good thing. Consider a restriction orifice downstream sized to limit the maximum flow within the meter range. A flow control loop would be better. This could restrict the outlet or recycle from the pump discharge back upstream on high flow. These options could also be costly.

Now about this ethanol, is it pure or denatured? Perhaps we may be able to find a way to afford the new meter after all.

John

 

[PAN]

jsummerfield,

The ethanol is 99.5% purity. Please advise us the difference in flowmeter selection.

We intend to adjust the valve at discharge of pump to control the maximum flow. This valve will be locked to avoid mis-operation. This should be the same basis of restriction orifice.

 

[jmw]

There are two main factors to consider regarding excess flow:
1) changes in meter factor: even PD meters will show some non-linearity
2) excessive wear: especially important with a non-lubricating fluid (what's good for throats is not necessarily good for meters).
Flow meters are often de-rated for non-lubricating fluids so take care if the meter was supplied for an alternative duty to the one you now intend to use it on.

Viscosity is another factor to consider.
Apart from its effect on slip flow (low viscosity fluids tend to produce more slip than high viscosity) high viscosity fluids often necessitate a different set of tolerances in the rotors than a low viscosity fluid. Changing the duty from low to high viscosity operation or visa versa needs checking with the manufacturers.
Variable viscosity fluids may require viscosity correction.

Nor should you neglect temperature when considering changing the meter duty. PD meters are calibrated for the intended operating conditions.

Pressure is more of a factor in single case meters than double case.
In a single case meter the pressure containment is provided by the flow measuring chamber and in double case meters the measuring chamber only sees the differential pressure across it. Pressure causes distortions of the pressure casing which can affect accuracy if this is a single case meter.
For fiscal applications you will see pressure (and for temperature) corrections required for two reasons:
(1)meter factor correction due to the distortion of the measuring chamber
(2) pressure effect on the fluid.
The significance of these effects is down to the application and the meter.

However, at your operating conditions pressure is probably not of any significance but you can easily refer all these questions to the manufacturer.

JMW

http://www.ViscoAnalyser.com